The majority of circadian rhythm experimentation focuses on the light entrainable oscillator in the SCN. However, it is becoming increasingly clear the mammalian timing system involves at least a second circadian clock, the feeding entrainable oscillator. It has recently been shown that circadian clock genes are present in regions of the brain outside of the SCN as well as in the periphery. Furthermore, these genes are transcribed in a circadian fashion. These oscillations have been shown in animals with intact SCN or in cultured tissue in which the oscillations were induced by some external synchronizer. This proposal will test the hypothesis that these known oscillations can be driven by a biological clock distinct from the LEO. Specifically, we hypothesize that the rhythm in gene expression will be entrained to daily meals in rats with SCN lesions. This would be suggestive of the involvement of the FEO, and entrainment of clock gene expression to meal time in a particular tissue would be suggestive of the mechanism and locus of the clock.